1. Field of the Invention
This invention relates to CIM (Computer Integrated Manufacturing) technology, and more particularly, to a supervisory parallel switching device which is designed for use with a CIM system including a host computer unit connected via an extended computer integrated unit to at least one equipment unit through an SECS-compliant (Semiconductor Equipment Communication Standard) serial communication link, for the purpose of allowing the equipment unit to be continuously under computer control even in the event of an unanticipated shutdown to the extended computer integrated unit.
2. Description of Related Art
The CIM technology is widely utilized in the semiconductor industry to provide a centralized computer control system of all the various fabrication processes in the factory where a large number of separate equipment units of different fabrication purposes are installed. In CIM technology, these separate equipment units are all linked to a host computer so that the various fabrication processes carried out through these equipment units can be centrally controlled. Conventionally, these equipment units are linked to the host computer unit through an SECS-compliant serial communication link, which allows control parameters and process status data to be exchanged between the host computer unit and each equipment unit.
FIG. 1 shows a conventional CIM system utilizing SECS-compliant serial communication links. As shown, this CIM system includes a host computer unit 10 and two equipment units 21, 22 (it is to be noted that in reality a CIM system may include several dozens of equipment units, but for purposes of simplification of illustration and description, only two equipment units are shown in FIG. 1). To allow the host computer unit 10 to control and monitor the fabrication process at each of the equipment units 21, 22, a first SECS-compliant serial communication link 21a is established between the host computer unit 10 and the first equipment unit 21, while a second SECS-compliant serial communication link 22a is established between the host computer unit 10 and the second equipment unit 22. Through the first SECS link 21a, the host computer unit 10 can issue control parameters to the first equipment unit 21 and receive process status data from the same, while through the second SECS link 22a, the host computer unit 10 can issue control parameters to the second equipment unit 22 and receive process status data from the same.
A drawback to the forgoing CIM system, however, exists because there are some problems when the host computer unit 10 is considered to increase supervisory functions without changing its original structure. That is if you attempt to change the original structure of the host computer unit 10 which controls the CIM system, the operation may stop, destroying the original system, and rendering the production procedure abnormal.
One solution to the foregoing problem is shown in FIG. 2. By this solution an extended computer integrated unit 30 is installed between the host computer unit 10 and each equipment unit 20. The extended computer integrated unit 30 is a separate computer unit which communicates with equipment unit 20 through a first SECS link 20a and communicates with the host computer unit 10 through a second SECS link 30a, and which is programmed to carry out dedicated data processing tasks specific to the linked equipment unit 20. As a result, the provision of the extended computer integrated unit 30 can help extend the supervisory capabilities of the host computer unit 10, allowing an overall increase to the throughput of the CIM system.
However, as shown in FIG. 3, the forgoing solution still has the drawback that in the event of an unanticipated shutdown to the extended computer integrated unit 30 due to, for example, power failure or system crash, it will disconnect the SECS links 20a, 30a and thereby put the equipment unit 20 beyond computer control, thus halting the current fabrication process at equipment unit 20. If equipment unit 20 is a crucial fabrication point, it would considerably affect the overall fabrication process over the entire CIM system.
One solution to the foregoing problem is to provide a software-based monitoring means in each extended computer integrated unit, which is capable of checking whether the data communication over the SECS link is normal or not. Thus, in the event of an extended computer integrated unit shutdown due to system crash, the software-based monitoring means would be capable of linking the associated equipment unit to the host computer unit. This solution would allow each equipment unit to be continuously under the control of the computer even when the associated extended computer integrated unit is in a shutdown state. However, this solution still has two drawbacks. Firstly, where the software-based monitoring means is not functioning, due, for example, to deadlock or power failure, it would be unable to reconnect the equipment unit to the host computer unit in the event of an extended computer integrated unit shutdown. Secondly, the design of software-based monitoring means requires the software developer to fully understand the SECS protocol and the data communication contents between the host computer and each particular type of equipment unit, which would make the development of communication links and content quite laborious and make the developed software program suitable for use with only a particular equipment type.
It is therefore an objective of this invention to provide a supervisory parallel switching device for use with a CIM system with SECS links, which can allow each equipment unit to be continuously under computer control even in the event of an unanticipated extended computer integrated unit shutdown.
It is another objective of this invention to provide a supervisory parallel switching device for use with a CIM system with SECS links, which is functional even in the event of a power failure.
It is still another objective of this invention to provide a supervisory parallel switching device for use with a CIM system with SECS links, whose design requires no understanding of the communication protocol and contents between the host computer unit and each equipment unit, and which is suitable for use with various types of equipment units.
The supervisory parallel switching device of the invention is designed for use with a CIM system including a host computer unit connected by a SECS-compliant serial communication link via an extended integrated computer unit to at least one other equipment unit, for the purpose of connecting, in the event of a shutdown, the second equipment unit directly to the host computer unit and to the extended computer integrated unit; wherein the host computer unit and the equipment unit each has a communication port of a standardized type, while the extended computer integrated unit has a first passthrough port and a second passthrough port. The supervisory parallel switching device of the invention comprises: (a) a set of connecting ports, including a first connecting port which is connected to the communication port of the host computer unit; a second connecting port which is connected to the second passthrough port of the extended computer integrated unit; a third connecting port which is connected to the first passthrough port of the extended computer integrated unit; and a fourth connecting port which is connected to the communication port of the equipment unit; (b) switching means capable of being selectively switched between a first switch position and a second switch position in such a manner that when being switched to the first switch position, the switching means connects the fourth connecting port to the first connecting port; and when being switched to the second switch position, the switching means connects the fourth connecting port to the third connecting port and meanwhile connects the first connecting port to the second connecting port; and (c) a control logic unit, capable of detecting whether the extended computer integrated unit is in a normal operating state or in a shutdown state. When the extended computer integrated unit is in a normal operating state, the control logic unit activates the switching means to be switched to the second switch position, thereby linking the equipment unit through the extended computer integrated unit to the host computer unit; and when the extended computer integrated unit is in a shutdown state, the control logic unit activates the switching means to be switched to the first switch position, thereby linking the equipment unit directly to the host computer unit.
Therefore, when the extended computer integrated unit operates normally, the equipment unit is linked through the extended computer integrated unit to the equipment unit. However, in the event of an unanticipated shutdown to the extended computer integrated unit, the equipment unit will be promptly linked to the host computer unit, thus allowing the equipment unit to be continuously under computer control by the host computer unit without being interrupted by the extended computer integrated unit shutdown.